Madhya Pradesh Police Exam Model Paper 6

Given:
Average marks obtained by 8 students = 51
Average marks obtained by 9 students = 68
Calculation:
Total marks obtained by 8 students $=51\times 8$
⇒ 408
Total marks obtained by 9 students $=68\times 9$
⇒ 612
The total marks obtained by 17 students $=408+612$
⇒ 1020
Required average $=1020/17$
⇒ 60
∴ The average marks of all the students are 60.